redlock

hold a lock on the same resource at the same time. The security of the lock is broken. The Redis authors have designed the Redlock algorithm for possible loss of lock security during Redis master-slave replication. The client that runs the Redlock algorithm performs the following steps in turn to complete the operation to acquire the lock : Gets the current time (number of milliseconds). The performs

of the lock was broken. To solve this problem, Antirez designed the Redlock algorithm. "Other questions" The effective time of the lock that appears in the previous algorithm (lock validity times) is set to how appropriate. If the setting is too short, locks are likely to expire before the client completes access to the shared resource, thereby losing protection, and if the setting is too long, if a client holding the lock fails to release the lock

of code, the Isopenexpirationrenewal property to False, and the thread polling to stop flushing the expiration time. public void unlock() { //... isOpenExpirationRenewal = false; } Full code for version 5: GitHub address3.7 Testing The test code is as follows public void testLockCase5() { //定义线程池 ThreadPoolExecutor pool = new ThreadPoolExecutor(0, 10, 1, TimeUnit.SECONDS,

code to the Jedis.eval () method and assign the parameter keys[1] to Lockkey, Argv[1] is assigned a value of RequestID。 The eval () method is to deliver the LUA code to the Redis server for execution. Five Redlock Redlock is an official Redis distributed lock principle. Official document Description: "There are a lot of tripartite libraries and articles describing how to implement a distributed lock

are as follows:Import randomsingle_cast_script= "" "Local channels = Redis.call (' pubsub ', ' channels ', argv[1] ... *‘); If #channels = = 0 then return 0; End Local index= Math.mod (Math.floor (Tonumber (argv[2)), #channels) + 1; Return Redis.call (' Publish ', Channels[index], argv[3]); Def wait_single (channel, myID): Return Wait (Channel + myID) def signal_single (channel, data): rand_num = Int (Random.ran Dom () * 65535) return Rc.eval (single_cast_script, 0, Channel, str (rand_num), st

prefix and unique ID into one channel name , and then wait the same as the previous example. Examples are as follows:Import randomsingle_cast_script= "" "Local channels = Redis.call (' pubsub ', ' channels ', argv[1] ... *‘); If #channels = = 0 then return 0; End Local index= Math.mod (Math.floor (Tonumber (argv[2)), #channels) + 1; Return Redis.call (' Publish ', Channels[index], argv[3]); Def wait_single (channel, myID): Return Wait (Channel + myID) def signal_single (channel, data): rand_nu

lock based on Redis, the Redlock algorithm is presented, and the implementation cases of many languages are listed, here is a brief introduction. The Redlock algorithm looks at three elements that meet distributed locks: Security: Guarantees mutual exclusion, at most at any time only one client can hold locks Deadlock free: Even if the client that is currently holding the lock crashes or is separated from

', $timeout, ' NX ');//ex sec if ($isLock) { if Redis:: Get ($key) = = $value) { //Prevent early expiration, mistakenly delete other requests created by the lock //Execute internal code redis::d El ($key); continue;//execution successfully deletes the key and jumps out of the loop } else { usleep (5000);//sleep, reduce the lock frequency, ease the redis pressure,

A distributed lock is a very useful primitive in many environments, and it is the only way to share resources between mutually exclusive operations of a process. There are a number of development libraries and blogs that describe how to implement DLM (distributed Lock Manager) using Redis, but each development library uses a different approach, and many libraries are implemented in simple, low reliable ways compared to more complex designs and implementations. This article attempts to provide a

problem is due to the use of master-slave replication, the solution is not to use the master-slave replication, using the Redlock algorithm, here refers to a section of the online description of the Redlock algorithm.In a REDIS distributed environment, assuming that there are 5 Redis master, these nodes are completely independent of each other, there is no master-slave replication or other cluster coordina

, but the master-slave replication mechanism is asynchronous, there will be data synchronization problems, may lead to multiple machines multiple threads to obtain the same lock; the solution is to use the master-slave replication caused by the problem, the solution is not the master-slave replication, using the Redlock algorithm; Redlock is described as follows: In a Redis distributed environment, ass

)) { if(redislock.isacquired) {work (); return true; } } return false; } } /// ///Reset Key/// /// /// Private stringCreateKey (stringkey) { return string. Join ("_", Rediscachebase.systemcode,"LOCK", key); } }}View CodeCall example, simple roughDistributedlockmanager lockmanager=NewDistributedlockmanager (); TimeSpan Expirytime=NewTimeSpan (0,3,0); BOOLIswork=lockmanager.overlappingwork

,redissonclient redisson2, redissonclient redisson3) { Rlock lock1 = Redisson1.getlock ("Lock1"); Rlock Lock2 = Redisson2.getlock ("Lock2"); Rlock Lock3 = Redisson3.getlock ("Lock3"); Redissonmultilock lock = new Redissonmultilock (Lock1, Lock2, LOCK3); try { //Lock at the same time: Lock1 Lock2 Lock3, all the locks were successfully locked. Lock.lock (); //Try to lock, wait up to 100 seconds, automatically unlock after 10 seconds of lock Boolean res = Lock.trylock (+, tim

"); Redissonmultilock lock = new Redissonmultilock (Lock1, Lock2, lock3); try { //simultaneous lock: Lock1 lock2 lock3, all locks are locked successfully. Lock.lock (); Try locking, wait up to 100 seconds, lock after 10 seconds automatically unlock boolean res = Lock.trylock (M, timeunit.seconds); Interruptedexception e) { e.printstacktrace (); } finally { lock.unlock (); } } 4. Red Lock (Redlock) The Redisson Redissonredlock object

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default. If the lock is not released, the lock will be automatically eliminated after 10 s. The value set when the lock is obtained is also saved. When the lock is released, the system first checks whether the saved value is the same as the current lock value. If not, it indicates that the lock is automatically released after expiration and is obtained by other processes. Therefore, the lock value must be unique to avoid releasing the lock obtained by other programs. Use lock: def a_to_b():

Reference link for Redis distributed locks: http://redis.io/topics/distlock.In our project, before pondering using: Servicestack.redis, found that Servicestack.redis charges, operating more than 6,000 times per hour error : "The Free-quota limit on ' 6000 Redis requests per hour ' has been reached ... "So look at other Redis clients:Stackexchange.redis seemingly does not support distributed locks , or I do not know?Redlock.net and Redlock-cs are bad f